环境地球化学国家重点实验室知识库

Total mercury (Hg) concentrations (THg) and stable mercury isotopic compositions were measured in coal samples (n = 61) from major coal producing fields in China. The THg concentrations in coals ranged from 0.05 to 0.78 mu g g(-1) with a geometric mean of 0.22 mu g g(-1) isotopic compositions in coals showed large variations both in mass-dependent fractionation (MDF, delta Hg-202: -2.36 to -0.14 parts per thousand) and mass-independent fractionation (MIF, Delta Hg-199: -0.44 to +0.38 parts per thousand). The MIF signatures in coals may reveal important information on the coal-forming conditions (e.g., humic and sapropelic). The Delta Hg-199/Delta Hg-201 of similar to 1 determined in coals indicated that a portion of Hg has been subjected to photoreduction process prior to being incorporated to coals. On the basis of THg, Hg isotopic signatures, and other geological factors (e.g., total ash content and total sulfur content), the potential sources of Hg in coals from different coal producing regions were estimated. The main source of Hg in coals from southwestern China and eastern part. of northern China is likely geogenic Hg, whereas the source of Hg in coals from other parts of northern China is mainly biogenic Hg. Finally, we estimated that Hg emission from coal combustion in China is characterized by diagnostic Hg isotopic signatures (delta Hg-202: similar to-0.70 parts per thousand and Delta Hg-199: similar to-0.05 parts per thousand). The present study demonstrates that Hg isotopes can serve as a tool in understanding the sources and transformation of Hg in coals and may also be used as a tracer to quantify Hg emissions from coal combustion.